# Magent NRPE — Natriuretic Response Prediction Equation (Rao 2021)

> Magent NRPE — Natriuretic Response Prediction Equation (Rao 2021) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Computes the predicted spot urine sodium output (mmol) ~2 hours after IV loop diuretic using the Rao 2021 natriuretic response prediction equation, and classifies response as poor, suboptimal, or excellent.

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/nrpe
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/magent-nrpe-natriuretic-response-prediction-equation-rao-2021-83d168b5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wZl4-5hkSRUm3UcrvrMne

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability magent-nrpe-natriuretic-response-prediction-equation-rao-2021-83d168b5
```

Example prompt: My patient has an eGFR of 42 mL/min/1.73m², BSA of 1.85 m², serum creatinine of 1.6 mg/dL, urine creatinine of 95 mg/dL, and a spot urine sodium of 68 mmol/L collected about 2 hours after IV furosemide — use the Rao 2021 natriuretic response equation to tell me if their diuretic response is poor, suboptimal, or excellent.

## When to prefer this

Use this endpoint when you need to apply the Rao 2021 NRPE formula specifically — i.e., you already have caller-computed eGFR and BSA and want to classify loop diuretic natriuretic response from a 2-hour spot urine sample. Prefer this over generic urine electrolyte tools when the clinical question is diuretic adequacy in the context of heart failure or volume overload management. Do not use this to compute eGFR or BSA — those must be provided by the caller.

## Known failure modes

- Missing required parameter (eGFR, BSA, or urine sodium) returns validation error
- Both serum creatinine units provided simultaneously (mg/dL and µmol/L) causes conflict error
- Both urine creatinine units provided simultaneously causes conflict error
- Out-of-range values (e.g. eGFR outside 5–200, BSA outside 0.4–3.5) return validation error
- Caller-provided eGFR or BSA is incorrect — endpoint does not validate or recompute these values
- Urine sample not collected at ~2h post-diuretic will produce a biologically invalid result without error

## How this service works

Rao 2021 natriuretic response prediction equation from caller-assigned eGFR and BSA, serum and urine creatinine, and urine sodium on a spot sample ~2 h after IV loop diuretic. Na_output_mmol = eGFR*(BSA/1.73)*(SerumCr/UrineCr)*60*3.25*(UrineNa/1000). Poor <50 mmol; suboptimal <100 mmol (includes poor); excellent >150 mmol. magent does not compute eGFR or BSA and does not order a diuretic.

## Output

Returns the predicted urinary sodium output in mmol using the formula Na_output_mmol = eGFR × (BSA/1.73) × (SerumCr/UrineCr) × 60 × 3.25 × (UrineNa/1000), along with a categorical classification: poor (<50 mmol), suboptimal (<100 mmol, includes poor), or excellent (>150 mmol).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "egfr_ml_min_1_73m2",
      "bsa_m2",
      "urine_sodium_mmol_l"
     ],
     "properties": {
      "bsa_m2": {
       "type": "number",
       "description": "Caller-assigned body surface area in m² (0.4-3.5). Paper used Du Bois. magent does not compute BSA."
      },
      "creatinine_mg_dl": {
       "type": "number",
       "description": "Serum creatinine in mg/dL (0.1-20). Provide this or creatinine_umol_l, not both."
      },
      "creatinine_umol_l": {
       "type": "number",
       "description": "Serum creatinine in µmol/L (9-1768). Converted as mg/dL = µmol/L / 88.42. Provide this or creatinine_mg_dl, not both."
      },
      "egfr_ml_min_1_73m2": {
       "type": "number",
       "description": "Caller-assigned eGFR in mL/min/1.73m² (5-200). magent does not compute CKD-EPI (including race-based 2009 CKD-EPI)."
      },
      "urine_sodium_mmol_l": {
       "type": "number",
       "description": "Spot urine sodium in mmol/L (1-300), ~2 h after IV loop diuretic."
      },
      "urine_creatinine_mg_dl": {
       "type": "number",
       "description": "Urine creatinine in mg/dL (1-500). Provide this or urine_creatinine_umol_l, not both."
      },
      "urine_creatinine_umol_l": {
       "type": "number",
       "description": "Urine creatinine in µmol/L (88-44210). Converted as mg/dL = µmol/L / 88.42. Provide this or urine_creatinine_mg_dl, not both."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/magent-nrpe-natriuretic-response-prediction-equation-rao-2021-83d168b5/health.json
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